Capacitor ignition device for internal combustion engines

ABSTRACT

A capacitor ignition device for combustion engines comprising a charging transformer which is equipped with a secondary winding which together with the pick-up winding as the primary winding forms a transformer, and the secondary winding of the charging transformer in series with a blocking diode is connected in parallel with the primary winding of an ignition transformer, in order that for each ignition spark generated during flow of the pick-up current in the pick-up winding through the transmission of energy in the primary winding of the ignition transformer, the spark head which is generated by discharge of the storage capacitor is prolonged by a spark tail.

United States Patent [1 1 Diener 1 i CAPACITOR IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES [75] inventor: Rudolf Diener, Zurich, Switzerland [73] Assignee: Autoelektronik AG, Chur,

Switzerland [22] Filed: Dec. 27, 1973 [21] Appl. No.: 428,710

[30] Foreign Application Priority Data Dec. 22, 1972 Switzerland 18786/72 [56] References Cited UNITED STATES PATENTS 4/1967 Quinn 123/148 E Phillips et a1 123/148 E July 8,1975

3,796,204 3/1974 Hohne et al l23/l48 E Primary Examiner-Wendell E. Burns Assistant ExaminerJames W. Cranson Attorney, Agent, or Firm-Edward .l. Brenner [57] ABSTRACT A capacitor ignition device for combustion engines comprising a charging transformer which is equipped with a secondary winding which together with the pick-up winding as the primary winding forms a transformer, and the secondary winding of the charging transformer in series with a blocking diode is connected in parallel with the primary winding of an ignition transformer, in order that for each ignition spark generated during flow of the pick-up current in the pick-up winding through the transmission of energy in the primary winding of the ignition transformer, the spark head which is generated by discharge of the storage capacitor is prolonged by a spark tail.

3 Claims, 2 Drawing Figures PATENTEDJUL 8 ms III] I Fig. 2

1 CAPACITOR IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION The present invention relates to a new and improved construction of capacitor ignition device or circuit arrangement for internal combustion engines wherein for each ignition spark a storage capacitor is charged with electrical energy stored during current flow through a take-up winding, by an output of a charging transformer forming an inductive storage by interrupting the pick-up current, and wherein upon ignition of a thyristor the storage capacitor is discharged through the primary winding of an ignition transformer. Further, a battery, the pick-up winding, the collector-emitter path of a transistor and the primary winding of a feedback transformer are connected in series, and the transistor circuit contains means for limiting the collector current to a maximum value in order to block the transistor in each case upon reaching a maximum collector current via the feedback transformer and thus to interrupt the current flow through the pick-up winding, and for the thyristor as well as the transistor there is provided a control pulse generator wherein for each ignition spark, by means of a control pulse, the thyristor is fired for discharge of the storage capacitor and for charging of the storage capacitor the transistor under the action of the feedback transformer is switched into its conductive state.

With capacitor ignition devices of such or similar simple construction the power losses and thus the inherent heating are negligibly small, which is of decisive importance for the good functional reliability of the ignition system since the ignition devices contain semiconductor elements and are arranged beneath the hood of the engine at the neighborhood of the engine where they oftentimes are heat-up to almost the permissible boundary temperature of the semi-conductor elements. The ignition sparks, which are independent of voltage fluctuations of the battery, are so strong that there is ensured for positive ignition. Owing to the stark or strong ignition sparks the spark plugs hardly tend to become covered with carbon or soot. The ignition sparks are of brief duration, generally amounting to 300 usec. With such brief and powerful ignition spark there is realized for many different types of engines a faultless and reliable ignition, but for some types of engines there are however required ignition sparks of longer duration. Prior art known capacitor ignition devices for generating relatively long ignition sparks contain as the storage capacity two capacitors which are continuously maintained in a charged condition by an oscillator, and specifically one such capacitor at a higher voltage, for instance 400 volts, and the other at a lower voltage, for instance 50 volts. Due to successive discharge of both capacitors through the primary winding of the ignition transformer there are produced ignition sparks each having a respective short, powerful spark head and a subsequent rather slow decaying spark tail. Such ignition devices are complicated and owing to the high power losses are generally subject to disturbances in operation.

SUMMARY OF THE INVENTION Hence, it is a primary object of the present invention to provide an improved construction of capacitor ignition device for combustion engines which is not associated with the afore-mentioned drawbacks and limitations of the prior art constructions.

Another and more specific object of the present invention relates to an improved construction of capacitor ignition device of the previously mentioned type for combustion engines for generating ignition sparks with a short, powerful spark head and a subsequent slower decaying spark tail.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the invention contemplates that the charging transformer is equipped with a secondary winding which together with the pick up winding as primary winding forms a transformer, and the secondary winding of the charging transformer in series with a blocking diode is connected in parallel with the primary winding of an ignition transformer, in order that for each ignition spark during flow of the pick-up current in the pick-up winding through the transmission of energy in the primary winding of the ignition transfonner the spark head which is generated by discharge of the storage capacitor is prolonged by a spark tail. The expenditure required for generating longer ignition sparks is thus only very slight and the advantages of faultless and reliable ignition with negligibly lower power losses remains practically unaltered.

With suitable dimensioning of an air gap present at the charging transformer, the inductance of the secondary winding of the charging transformer as well as the inductance of the primaryand secondary windings of the ignition transformer as well as the electrode spacing of the spark plugs, it is possible to easily prolong the duration of the spark tail to four to five times the duration of the spark head, so that ignition spark exceeding 1.5 msec duration can be obtained, by means of which the gas which has been compressed in the cylinder, for practically all encountered situations, can be ignited for good combustion thereof.

It can happen that for the primaryand secondary windings of the ignition transformer designed for a long ignition spark duration the transmission ratio is too low for a desired height of the spark head. Therefore the primary winding of the ignition transformer is advantageously formed of two partial windings which are connected in series with the secondary winding and wherein one partial winding is electrically connected to the storage capacitor, so that for generating a powerful spark head the storage capacitor is only discharged through this partial winding, whereas both partial windings have current flowing therethrough from the secondary winding of the charging transformer.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes references to the annexed drawing wherein:

FIG. 1 is a circuit diagram of a simple constructional embodiment of capacitor ignition device designed according to the teachings of the invention; and

FIG. 2 illustrates the oscillogram of a long ignition spark obtained with the capacitor ignition device of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now the drawing, with the ignition circuit depicted in FIG. 1 the pick-up coil or winding 1a of a charging transformer 1, which possesses an iron core 1d, is connected at its one end or terminal by an ignition switch Z with the positive pole of a power source, here the battery B and at its other end or terminal by means of the collector-emitter path of a transistor Tr and the primary winding 2a of a feedback transformer 2 with ground. The negative pole or terminal of the battery B is likewise connected with ground, as shown. A resistor R, connects the emitter of the transistor Tr with its base which is electrically coupled with a control pulse generator or transmitter 6. The secondary winding 2b of the feedback transformer 2, the iron core 2c of which is not saturated for the current intensities which prevail at the primary winding 20, is likewise connected between the emitter and the base of the transistor Tr. A control thyristor is provided to serve as a means for limiting the collector current to a predetermined maximum value. As shown in FIG. 1, the anode of the control thyristor 5 is connected with the base of the transistor Tr and its cathode is connected with ground. A voltage divider composed of the resistor R and R, is connected in parallel with the control thyristor 5, and at the junction point of this voltage divider R,,, R, there is connected the control electrode of the control thyristor 5, as shown, so that the control thyristor 5 fires or ignites as soon as the collector current has reached that intensity at which the base current of the transistor Tr generates at the voltage divider R R the firing or ignition voltage for the thyristor.

The output or delivery winding lb of the charging transformer 1, as is usual for such ignition circuits, is connected with its one end or terminal with the pick-up winding la and at its other end or terminal via a diode D, with a storage capacitor C,, the other capacitor plate or coating of which is connected via the primary winding 30' of an ignition transformer 3 with ground. The secondary winding 3b of the ignition transformer 3, through the agency of a distributor, supplies the spark plugs of the internal combustion engine, which have only been indicated in FIG. I by a spark gap or path 8. To discharge the storage capacitor C, through the primary winding 3a of the ignition transformer 3 there is provided the thyristor 4, the anode of which is coupled with the storage capacitor C, and the cathode of which is connected with ground. The ignition electrode of the thyristor 4 is connected with ground by means of a resistor R, and is additionally connected with the control pulse generator 6 which is controlled by the interrupter 7 such that upon opening the interrupter contacts it always delivers a control pulse. Such control pulse generators are known in the art, and one control pulse generator which is particularly suitable for this ignition circuit has been disclosed, for instance, in Swiss Pat. No. 518,035, or in US. Pats. Nos. 3,677,254 and 3,678,299. By means of the ignition circuit, to the extent that such has been described up to now, there are obtained ignition sparks of short duration. In the oscillogram of PK]. 2 there are shown such short ignition sparks by means of the broken-line curve III.

in order to generate longer ignition sparks the charging transformer 1 possesses a secondary winding 1c which together with the pick-up winding or coil 1a forms a transformer or transducer. The one end of the secondary winding 10 is connected with ground and the other end or terminal thereof is connected via a blocking diode D with the primary winding of the ignition transformer 3. In the illustrated exemplary embodiment the primary winding of the ignition transformer 3 consists of two partial windings or coils 3a, 3a (windings with taps) which are connected in series, wherein the connection point or junction of both such partial windings is connected with the storage capacitor C, and the free end of the partial winding 30 is coupled via the blocking diode D, with the secondary winding 10, so that the capacitor C, only discharges through the partial winding 3a, and both partial windings 3a, 3a together with the blocking diode D and the secondary winding 1c of the charging transformer 1 form a current circuit which is connected with ground. For dampening feedback oscillations both of the windings 3a, 3a are bridged by a diode D If after closing the ignition switch Z there is delivered for the first time a control pulse, due to opening of the interrupter contacts 7, to the base of the transistor Tr by means of the control pulse generator 6, then the transistor Tr becomes conductive and current flows from the battery B through the pick-up winding 1a of the charging transformer l, the collector-emitter path of the transistor Tr and the primary winding 2a of the feedback transformer 2. Due to the slight current flow in the primary winding 2a of the feedback transformer 2 a current is induced in its secondary winding 2b, by means of which the transistor is rapidly switched into its completely conductive state, so that the current flowing through the pick-up winding la of the charging transformer l rapidly increases. The current increase is determined by the air gap which is present at the core 1d of the charging transformer l and the inductance of the pick-up winding la, the secondary winding 10 as well as the primary winding of the ignition transformer 3. A part of the electrical energy which has been takenup by the pick-up winding or coil la is used for the excitation of the air gap and another part of this electrical energy is consumed in the current circuit composed of the secondary winding 10, the diode D the primary winding of the ignition transformer and ground. if the current flowing through the pick-up winding la reaches an intensity such that by means of the transistor base current the voltage drop at the voltage divider R R is so large that the control thyristor 5 tires or ignites, then the voltage at the base of the transistor Tr breaks down and the transistor Tr is rapidly brought into its blocked or non-conductive state via the feedback transformer 2. The current flow through the pick-up winding 1a is interrupted and the energy stored at the charging transformer 1 drives the voltage at the pick-up winding lb and output winding respectively, to about 400 volts. The storage capacitor C, is charged through the agency of the diode D, and the diode D With the interrupter contacts closed the the storage capacitor is charged. With renewed opening of the interrupter contacts 7 the thyristor 4 is tired by a control pulse of the control pulse generator 6, so that the storage capacitor C discharges through the conductive thyristor 4 to ground and from ground through the primary winding 3a of the ignition transformer 3 and in the secondary winding 3b of such ignition transformer there is induced a high voltage, which during the ignition sparks of the spark plugs generates a pronounced spark head I (FIG. 2). At the same time by means of the control pulse the transistor Tr, as already mentioned, is rendered conductive and immediately thereafter the current flow through the pick-up winding la is interrupted. The increase of the current flow in the pick-up winding la of the charging transformer l induces a current at the secondary winding lc which additionally flows through the primary winding 3a, 3a of the ignition transformer 3 and produces the spark tail ll (FIG. 2) during the ignition sparks.

With such capacitor ignition device it has been possible to realize satisfactory results. Thus, for instance, with an experimental capacitor ignition device for short ignition sparks during charging of the storage capacitor to 400 volts, an inductance of the primary winding of the ignition transformer of mH, a transformer ratio of the ignition transformer of 1:50, a spark plugelectrode spacing of 1 mm and a gas pressure of 10 atmospheres the spark duration amounted 300 u see. The same ignition device was equipped with the afore mentioned components for prolongation of the sparks. The sparks duration then amounted to a total of 1050 a sec. Measurements of the fuel consumption with an Otto cycle engine equipped with the capacitor ignition device for long ignition sparks, in contrast to the conventional ignition, produced a gas consumption which was less by 10 to 18 percent, something which was especially attributable to the fact that the fuel-air mixture was always ignated and burned well and that there was not ejected any non-combusted fuel.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,

What is claimed is:

l. A capacitor ignition arrangement for an ignition combustion engine having spark plugs, comprising an ignition transformer including primary winding means and a secondary winding connectable with each of the spark plugs;

a storage capacitor;

a thyristor having a control electrode;

means connecting together said thyristor to form a discharge path for said storage capacitor, discharging of the storage capacitor through said discharge path producing a high voltage firing pluse across the spark plug connected with the secondary winding of said ignition transformer;

a charging transformer having a pick-up winding and an outputwinding on a ferromagnetic core;

means connecting together said storage capacitor and said output-winding to form a charging path for said storage capacitor;

a source of direct current;

a transistor having an emitter, a collector, and a base;

means connecting in series said source of direct current, said pick-up winding, and the collectoremitter path of said transistor, so that when said transistor is conductive, current flows through the pick-up winding and electrical energy is stored in said charging transformer, and when current flow is interrupted by blocking said transistor the stored energy is delivered via said charging path to said storage capacitor;

a control pulse generator synchronized with said engine; and a control circuitry responsive to control pulses delivered from said control pulse generator, said control circuitry including said transistor, switch-on means for triggering conductive said transistor with each control pulse, and cut-off means sensitive to the strength of the collector current of said transistor to block the transistor upon reaching a maximum collector current, and also having an output connected with the control electrode of said thyristor so that with each control pulse said thyristor is triggered conductive and a firing pulse is delivered,

wherein the charging transformer is equipped with an additional winding, said additional winding and the pick-up winding of said charging transformer forming a transducer which delivers electrical energy when current flows through said pick-up winding, and

wherein said additional winding, a blocking diode and the primary winding means of the ignition transformer are connected in series, so that each firing pulse produced by discharging of the storage capacitor is prolonged by an after-discharge of electrical energy delivered from said transducer.

2. The capacitor ignitiondevice as defined in claim 1, wherein said charging transformer, comprising the ferromagnetic core, the pick-up winding, the output winding and the additional winding, has an air gap, the size of the air gap together with the inductance of the additional winding and the inductances of the primary winding means and the secondary winding of the ignition transformer as well as the spark plug electrode spacing determining the duration of the afterdischarge.

3. The capacitor ignition device as defined in claim I, wherein the primary winding means of the ignition transformer comprise two partial windings which are connected in series with the blocking diode and the additional winding of the charging transformer, one of the partial windings being connected with the storage capacitor, so that the storage capacitor is discharged only through said one partial winding of the primary windin g means. 

1. A capacitor ignition arrangement for an ignition combustion engine having spark plugs, comprising an ignition transformer including primary winding means and a secondary winding connectable with each of the spark plugs; a storage capacitor; a thyristor having a control electrode; means connecting together said thyristor to form a discharge path for said storage capacitor, discharging of the storage capacitor through said discharge path producing a high voltage firing pluse across the spark plug connected with the secondary winding of said ignition transformer; a charging transformer having a pick-up winding and an outputwinding on a ferromagnetic core; means connecting together said storage capacitor and said output-winding to form a charging path for said storage capacitor; a source of direct current; a transistor having an emitter, a collector, and a base; means connecting in series said source of direct current, said pick-up winding, and the collector-emitter path of said transistor, so that when said transistor is conductive, current flows through the pick-up winding and electrical energy is stored in said charging transformer, and when current flow is interrupted by blocking said transistor the stored energy is delivered via said charging path to said storage capacitor; a control pulse generator synchronized with said engine; and a control circuitry responsive to control pulses delivered from said control pulse generator, said control circuitry including said transistor, switch-on means for triggering conductive said transistor with each control pulse, and cut-off means sensitive to the strength of the collector current of said transistor to block the transistor upon reaching a maximum collector current, and also having an output connected with the control electrode of said thyristor so that with each control pulse said thyristor is triggered conductive and a firing pulse is delivered, wherein the charging transformer is equipped with an additional winding, said additional winding and the pick-up winding of said charging transformer forming a transducer which delivers electrical energy when current flows through said pick-up winding, and wherein said additional winding, a blocking diode and the primary winding means of the ignition transformer are connected in series, so that each firing pulse produced by discharging of the storage capacitor is prolonged by an after-discharge of electrical energy delivered from said transducer.
 2. The capacitor ignition device as Defined in claim 1, wherein said charging transformer, comprising the ferromagnetic core, the pick-up winding, the output winding and the additional winding, has an air gap, the size of the air gap together with the inductance of the additional winding and the inductances of the primary winding means and the secondary winding of the ignition transformer as well as the spark plug electrode spacing determining the duration of the after-discharge.
 3. The capacitor ignition device as defined in claim 1, wherein the primary winding means of the ignition transformer comprise two partial windings which are connected in series with the blocking diode and the additional winding of the charging transformer, one of the partial windings being connected with the storage capacitor, so that the storage capacitor is discharged only through said one partial winding of the primary winding means. 